Dental caries is essentially a microbial disease of childhood and is a major health problem in our society. Considering the bacterial nature of dental plaque and the current knowledge of the role of Streptococcus mutans in the etiology of dental caries, it is logical to predict that of all the approaches to the control of caries the antimicrobial route, especially the use of antibiotics could be one of the most effective. This proposal is concerned with an in depth study of the potential usefulness of highly specific antimicrobial agents, the bacteriocins, for the control of dental caries. Microorganisms that produced bacteriocins lethal to S. mutans will be identified. Bacteriocins which are active against all serotypes of S. mutans and yet are highly resistant to proteolytic enzymes will be selected for isolation and purification studies. The purified bacteriocins are to be tested in animal models to determine their ability to inhibit caries induction by eliminating the microorganisms which are the etiological agents. This approach is based on the expectation that these bacteriocins will eradicate the causative organisms when applied locally in the oral cavity, like antibiotics. The advantages of this novel approach are numerous but the chief advantage is derived from the fact these agents, unlike antibiotics, are highly selective with an extremely narrow spectrum of activity and hence will not adversely affect the normal ecologic balance of the oral microflora.